五螺箍筋混凝土柱雙曲率剪力撓曲反覆載重試驗研究

Double-Curvature Cyclic Shear and Flexural Behavior of Concrete Columns with Five-Spiral Reinforcement

李哲諺(Jhe-Yan Li)

指導教授 ： 歐昱辰

國立臺灣大學/工學院/土木工程學研究所/碩士(2020年)

https://doi.org/10.6342/NTU202003719

摘要

五螺箍筋運用在正方形斷面鋼筋混凝土柱已證實具有優於傳統方箍筋的圍束能力。若在建築物上使用五螺箍筋柱，將能提高建築物之耐震性能，且能減少鋼材的用量，達到環保之目標。本研究目的在於探討五螺箍筋之剪力與撓曲行為與破壞模式，設計試驗以觀察五螺箍筋極限狀態時之行為，並分析試驗結果數據。
為了模擬柱受側向載重之情形，本研究使用國家地震中心(NCREE)之多軸向測試系統(MATS)進行定軸力雙曲率反覆載重試驗，測試大型五螺箍柱與傳統方箍柱對照組。試體可分為剪力破壞與撓曲破壞兩大類，總共八座大型試體進行試驗。縱向鋼筋及橫向鋼筋皆使用設計降伏強度為420MPa之鋼筋，混凝土選用設計抗壓強度49MPa。試驗之變數包括橫向鋼筋形式、軸力大小、極限狀態破壞模式。
測試結果指出，箍筋體積比相同、鋼筋降伏強度與混凝土抗壓強度相似的情況下，剪力試體五螺箍柱展現稍弱於傳統方箍柱的極限剪力強度，所有五螺箍柱過最大剪力強度後力量衰退速率皆小於傳統方箍柱。高軸力五螺箍柱之破壞模式為箍筋拉斷，而高軸力傳統方箍柱之破壞模式為彎鉤鬆脫導致過早破壞；撓曲試體方面，依照現行規範之最小鋼筋量設計，五螺箍柱能發展高於傳統方箍之側向強度，並能達到更高之位移比，無論高低軸壓均有良好之韌性。
本研究另外發展一套改進離散計算剪力模型用來計算五螺箍柱剪力強度。與試驗結果比較，改進離散計算剪力模型能保守估計五螺箍剪力強度，此外，本模型具有與規範剪力公式用於傳統方箍剪力強度之相似保守程度。

關鍵字

鋼筋混凝土 ； 五螺箍 ； 雙曲率 ； 反覆載重 ； 離散計算剪力模型 ； 耐震

並列摘要

Five-spiral transverse reinforcement for square reinforced concrete columns has been proven to possess a confinement capability superior to that of conventional rectilinear tie reinforcement. Seismic performance of buildings can be improved by applying five-spiral reinforcement to columns. Additionally, environmental protection goals are reached via reducing the usage of reinforcing steel. The objective of this research is to investigate the shear and flexural behavior and failure modes of five-spiral reinforcement. Experiment was conducted to observe the extreme condition of columns also analyzed test results.
To simulate a column under lateral load, the Multi-Axis Testing System located in National Center of Research on Earthquake Engineering was chosen to carry out a double-curvature lateral cyclic loading experiment with constant axial load. Eight large-scale columns were tested, including four five-spiral columns and four comparable conventional tied columns. Specimens can be divided into shear-critical columns and flexural-critical columns. All design yielding strength was 420 MPa while the nominal compressive strength of concrete was 49 MPa. Variables included the type of transverse reinforcement, axial load ratio, and failure mode.
Test results showed that with the same amount and similar yield strengths of shear reinforcement and concrete compressive strengths, the shear-critical column with five-spiral reinforcement exhibited a slightly lower shear strength than the counterpart tied column. All the five-spiral columns showed a lower speed of strength degradation after the peak load than counterpart tied columns. Failure of the five-spiral column under a high axial load was caused by fracture of the spirals. In contrast, failure of the rectilinear tie reinforcement was caused by premature failure of the hook anchorage. For the flexural-critical column that was designed based on minimum requirement of transverse reinforcement, five-spiral column exhibited higher lateral strength than the rectilinear tied column and reached higher drift. All flexural-critical columns performed good ductility.
A modified Discrete Computational Shear Strength (DCSS) model was developed in this research for calculating the shear strength of five-spiral reinforcement. Comparison with the test results showed that the modified DCSS model provides conservative estimation of shear strength contributed by five-spiral reinforcement. Moreover, the DCSS model provides a degree of conservatism similar to the code equation for tie reinforcement.

並列關鍵字

Reinforced concrete ； Five-spiral reinforcement ； Double-curvature ； Cyclic ； Discrete computational shear strength model (DCSS) ； Seismic

參考文獻

[1] 翁正強、尹衍樑、王瑞禎、梁景裕、郭美婷（2010）。五螺箍矩形RC柱之軸壓試驗與優化設計研究。結構工程，25(1)，71-105。

[2] 翁正強、尹衍樑、王瑞禎、梁景裕、林光奕（2011）。五螺箍矩形RC柱之反復載重試驗與耐震性能。結構工程，26(1)，57-91。

[3] 劉羿慶（2018）。鋼絞線主筋柱之反覆載重行為。國立臺灣科技大學營建工程系碩士論文，台北市。

[4] 徐文基（2019）。無預力鋼絞線主筋混凝土柱反復載重行為。國立臺灣大學土木工程學研究所碩士論文，台北市。

[5] ACI Committee 318., American Concrete Institute., International Organization for Standardization. (2008). Building code requirements for structural concrete (ACI 318-08) and commentary. Farmington Hills, Mich： American Concrete Institute.